The present invention is concerned with polyurethane-modified, water-soluble enzymes, as well as with a process for the preparation thereof.
It is known to modify proteins, such as enzymes, in order to improve certain properties of the proteins, for example certain physical-chemical properties, such as the solubility in a desired system (for example an analytical reagent), the storage stability, compatability in a hydrophobic medium (for example in the case of binding to synthetic resin surfaces) or the biological properties, such as increasing the half life time of a protein in plasma, the reduction of the antigen action and the activity in a non-aqueous system, especially in an organic solvent.
From Federal Republic of Germany Patent Specification No. 27 55 053, it is known to modify biologically-active proteins by reaction with a urethane polymer. According to this, a biologically-active protein and a liquid polyurethane pre-polymer which is at least dispersable in water are reacted under substantially water-free conditions to give a solution which is then dispersed in water. It is a disadvantage of this process that, for example, the biologically-active protein must be used as a dry powder because otherwise, because of the reactivity of the NCO groups with water, a foam or a highly cross-linked product is formed; furthermore, only pre-polymers can be used which are already water-soluble. In addition, due to the heterogeneous reaction of a water-free protein with the pre-polymer, as a rule the activity is greatly reduced or even completely destroyed.
It is an object of the present invention to provide a polyurethane-modified enzyme, as well as a process for the preparation thereof which avoids the above-mentioned disadvantages and with which a modified enzyme is made available which, in particular, has the desired solubility properties and biological properties and can be obtained with a substantially improved activity yield.